1. Field of The Invention
The present invention relates generally to a textile dyeing method and apparatus. In particular, the invention relates to a modified dyeing method and apparatus comprising an automated analysis system The modified dyeing process reuses the conventionally wasted dyebaths.
2. Description of Prior Art
The textile industry is a major consumer of water. Approximately 160 pounds of water are required to produce one pound of textile product. Most of the 100 billion gallons of water used by the textile industry each year are consumed primarily in the dyeing and finishing processes for the textiles, namely yarn, fabric and carpet. The vast majority of this water is discharged to the sewer. The waste water, or dyebath, includes dissolved and suspended organic and inorganic chemicals, and, thus, the conventional dyeing process places a significant demand on water resources as well as waste treatment facilities, especially in areas such as Dalton, Ga., where carpet manufacturing plants are highly concentrated.
In a batch dyeing process, one piece (or several pieces) of the textile product is dyed in a vessel containing the dyebath. The bath is agitated or stirred and/or the textile product is tumbled in the bath so that the single dyebath has repeated contact with each portion of the textile product. The vessel may be pressurized, and heat is added to the bath to provide the desired temperature/pressure/time cycle for the dyeing. The piece of textile is then rinsed and removed from the vessel so that another batch may be dyed, and the depleted dyebath is discarded. The textile material is then dried and/or processed further on other production equipment.
In a continuous dyeing process, a piece of textile product is passed lengthwise through one or more pieces of machinery constituting a dye line or dye range. Subsequent pieces of product are sewn together to form a continuous chain of material proceeding through the dye range. The textile material may be exposed to multiple baths (typically of higher concentration than in batch dyebaths), rinses, and drying stages along its path, but it encounters each stage in succession and for a limited time in each.
Typically, continuous dye processes provide economies of scale and are attractive for larger production lot sizes in a particular color, whereas batch dye processes provide manufacturing flexibility and economic benefits in the case of small lot sizes. Certain products are also more amenable to either continuous or batch dyeing processes.
The nature of the batch dyeing process for textiles is especially wasteful. In the conventional batch dyeing processes, the dyebath is used only once per dye cycle, then discharged to the sewer. In addition, the valuable auxiliary chemicals mixed in the dyebath are lost with each discharged batch of water, which themselves place significant loads on the waste treatment system.
Both continuous and batch dyeing processes are common for broadloom carpets. Continuous dyeing offers cost advantages and greater ease in obtaining uniform color over a large production lot size. In contrast, batch dyeing is now used predominately for heavy-weight, high-end carpets which cannot be dyed as well with a continuous processes. Batch processes also offer the advantage of production flexibility due to the small lot size.
The conventional batch dyeing of nylon broadloom carpets is typically performed in an atmospheric vessel, or beck. Water, auxiliary chemicals, dyes and the carpet are loaded in the beck, with the carpet sewn in a loop so that it continuously enters and exits the dyebath, providing agitation and bath-to-carpet contact. The bath is slowly heated and then held at a specified, critical dyeing temperature for a given amount of time. Both the temperature and hold time are product dependent. As the bath is heated, the dyes penetrate the fiber of the carpet and form chemical bonds. The elevated bath temperature is held for a sufficient period of time to permit the dyes to migrate to a uniform distribution over the carpet, producing a level dyeing. A patch check on the carpet is then performed, and if the carpet is properly shaded, the bath and carpet are then diluted with fresh water to bring the carpet to a temperature acceptable for handling. The carpet is then removed, and the bath including virtually all of the auxiliary chemicals and any residual dyes is drained to the sewer. Several disadvantages of this conventional process are that it consumes excessive water, wastes the stored thermal energy in the dyebath, and releases dyes and auxiliary chemicals to the waste stream.
The dye used in the batch dyeing process is typically a mixture of three components--yellow, red and blue--with a ratio and total quantity selected to give the designed color for the textile product. The auxiliary chemicals used in the batch dyeing process typically include wetting agents, pH control agents, leveling agents, chelating agents, and others which aid the dyeing process, but are not consumed during the dyeing process like the dyes are consumed.
Generally, by the time the finished color of the carpet is achieved in the conventional batch dyeing process, the dyebath has undergone several changes. The dyebath temperature is about 200.degree. F., in contrast to the initial starting, ambient temperature of about 60.degree. F. There has been a small amount of dilution to the dyebath due to condensate of the injected steam, the preferred mode of heating. Most but not all of the dye has been transferred from the bath to the carpet fiber, but the auxiliary chemicals are essentially unchanged, and remain in the bath.
This spent dyebath, destined for the sewer in the conventional process, represents a significant investment of energy and chemicals which are available for reuse. Dyebath reuse offers the opportunity to reduce the consumption of water resources, to reduce energy consumption in the dyehouse, to conserve/reuse expensive auxiliary chemicals, and to reduce environmental pollution. There is also the potential for production rate increases due to reduced heatup times required by the present invention.
Presently, only for certain combinations of dyes and fibers, there is the possibility to reuse spent dyebaths in subsequent dyeings. However, for these combinations the amount of residual dye left in the baths is generally sufficient to result in off-shade dyeings of subsequent batches. Therefore, for these combinations, the concentration of residual dye for each of the component dyes must be accurately determined, and the recipe for the next dyeing be adjusted accordingly.
Dyebath reuse with manual intervention has been demonstrated on a limited scale for a wide variety of textile products. Yet the barrier to industry-wide implementation is the human involvement required to implement dyebath reuse. A trained chemist is necessary to collect test samples at the end of every dye cycle. The samples must then be transported to an equipped laboratory and analyzed for dye concentrations, and the corrected recipe calculated. It simply is not practical to have personnel on hand round-the-clock to perform these analyses since it can be difficult to find trained chemists willing to work on all shifts, and the employment costs are prohibitive. Further, the human involvement may also lead to analysis and/or calculation errors. Therefore, a solution to this problem is to automate the dyebath analysis process, which the present invention provides.
Various methods and apparatus are known in the textile industry that attempt to relieve some of the disadvantages of the conventional batch dyeing process. For example, U.S. Pat. No. 3,807,872 to Pronier. entitled "Process For Regulating The Concentration Of A Bath Of Dye Or Coloring And Equipment For Implementing This Process" discloses a method and apparatus to control concentration of a dye in a dyebath linearly over time. As disclosed, the first step is the preparation of the dyebath using all the additives except the dye substances. Then a certain volume of the dyebath is taken to act as a pure reference sample. Selected coloring agents are then added to the dyebath and in this way an initial real bath is obtained for dyeing the article. From this real bath, a certain volume is drawn off to form an initial mixed sample. A theoretical consumption curve is simulated by adding steadily and continuously to the initial mixed sample a certain amount of the pure sample. A continuous and steady flow is extracted from the mixed sample and directed to an analysis vessel. Simultaneously, a steady and continuous flow of liquid from the real bath, to which the article to be dyed is added, is directed to a second analysis vessel. Then through analysis, for example, by colorimetry, the liquids passing through the vessels are analyzed. When a difference is detected between the analysis signal corresponding to the mixed sample and real sample, the equilibrium parameters of the real bath are modified in order to cancel out the difference between the two signals.
Specifically, Pronier describes the desire to regulate the rate of change of dye concentration in a bath while the dyeing progresses. It suggests that the rate be regulated by temperature control with regulation efforts which compare the changing color of the dyebath to the changing color of a reference solution. Pronier changes the color of the reference at a linear rate by dilution.
While Pronier describes a desire to make optical measurements on a continuous sampling basis, it describes reasons that this cannot suitably be achieved. Further, the disclosure of Pronier makes clear that the technique does not involve the absolute measurement of the color of the bath. The present invention's automated analysis system has the capabilities to make the measurements which Pronier suggests can not be done; it can accurately measure the color spectrum of the bath and, therefore, can compute the concentration of each of the individual component dyes. Further, the present invention measures spent dyebaths for reuse in a completely different application of dyebath analysis than Pronier provides, and one for which Pronier is not suitable.
U.S. Pat. No. 3,966,406 to Namiki et al., entitled "Process For Jet Dyeing Fibrous Articles Containing Polyester-Type Synthetic Fibers" discloses a hot start jet dyeing process wherein a solution is prepared and heated in a preparation tank which is separate, but attached to, a dyeing tank so as to feed the dyes to the dyeing tank. A dyeing preparation tank is equipped with a heater to heat the dye liquor in the tank. First warm water and the fibrous articles are placed in the dyeing tank. The dyeing tank is then heated to at least 110.degree. C., preferably up to a 130.degree. C. Dyes and other chemicals are dissolved to disperse in water in the dye preparation tank, heated to 100.degree. C. and then put into the dyeing tank which is maintained preferably at 130.degree. C. while moving the fibrous article to be dyed in the bath at a rate of 80 to 300 meters/min.
Yet Namiki et al. does not disclose a hot-start process that involves reuse of the dyebaths, one process of the present invention, described infra. It also is specifically designed for polyester fibers, which are dyed at much higher temperatures, and under pressure to keep the bath from boiling away, than nylon which the present invention is more suitable to dye. Starting the dyeing process "hot" for polyester does not present the same challenges that are encountered with nylon.
U.S. Pat. No. 4,104,753 to Schuierer, entitled "Processes And Apparatus For The Batch Wet Treatment Of Textile Material" discloses batch dyeing of textile materials wherein during each circuit of textile immersion into a dyebath, the textile material moves from a liquor bath and is freed from the adhering surplus dye liquor to a large extent by a nozzle system feed with compressed air. The textile materials are then shock cooled by a cold water sprinkler prior to discharge from the dyeing tank. In this manner, the dyebath does not need to be cooled before the textile materials are discharged, and the dyebath may be reused in hot form.
Schuierer describes a batch dyeing system which first removes the fabric without cooling the bath, and then subsequently cools the fabric, and does not address the issues of quality defects which might be introduced to the product by these thermal shocks. Unlike Schuierer, in relation to the process of hot-termination of the present invention, described infra, the present invention is not interested in "How do you stop the process hot?" but "How do you get a good product if you do?" This is a challenge in the nylon carpet dyeing process not addressed in Schuierer. Further Schuierer does not disclose reuse of the bath that produces a quality product.
U.S. Pat. No. 4,152,113 to Walker et al., entitled "System For Dyeing Hosiery Goods" discloses a system for batch dyeing hosiery goods where the dyebath is recycled and reused in successive dyeing cycles. The dyebath unabsorbed by the hosiery goods is removed from the dye vat or container and directed to a waste water holding tank. Subsequently, spent rinse and finish waters are transferred from the vat to a waste water holding tank after the various rinse and finish operations. Periodically, the waste fluids are directed to a treatment zone where they are clarified sufficiently for utilization in the bath, rinse and finish operations in subsequent dyeing cycles. A small amount of the dyebath directed from a dye waste tank back to a machine via line for a subsequent dyeing cycle is diverted through a line and analyzed by instrumentation to determine the quantities and colors of the various dyes that must be added to result in a desired dye shade of the hosiery goods.
Walker et al. describes a process to clean up dyeing waste water so that it can later be reused. The Walker et al. process specifically attempts to remove the residual dye from the spent bath during the treatment process. The present invention does not rely on a waste treatment system. Instead, it reuses as much of the water, residual dye, auxiliary chemicals, and energy as possible by adding the necessary makeup chemical and dye quantities to make the bath suitable for the next batch. This approach requires the use of an analysis system to reveal the makeup quantity of dye required, but offers greater reuse benefits and avoids the treatment system capital and operating costs.
U.S. Pat. No. 4,350,494 to Scheidegger et al.. entitled "Process For The Dyeing Of Textile Material And Apparatus For Carrying Out The Process" discloses batch dyeing of carpet materials, as well as reconditioning and reuse of the exhausted dyebath. The process is characterized in that during dyeing the pH value is lowered, by the addition of an inorganic acid, by at least one unit of pH value. A liquid circulating system is provided including pH monitoring means and dosing means for automatically adding the necessary make-up chemical agents.
Scheidegger et at describes a process in which pH adjustments are used in an attempt to get all of the dye to be taken up by the product so that there is no residual dye in the spent bath. In the commercial batch processes for nylon carpet of the present invention, there is a small but significant quantity of residual dye in the spent baths. This amount cannot be ignored in a dyebath reuse process without off-shade dyeing in subsequent batches. The present invention operates successfully even if all of the dye happens to be taken up by the product, but also offers the flexibility of being able to deal with the residual dyes that are more typically encountered.
In view of the prior art it can be seen that there is a need for a modified dyeing process incorporating an automated analysis system that reuses the conventionally wasted dyebaths. It is to the provision of such a method and apparatus that the present invention is primarily directed.